DESCRIPTION: The goal of this project is to standardize the Micronucleus (MN) Assay in the eye lens to permit its utilization as a means to evaluate low level radiation exposure of individuals. The method has the potential to provide first approximations or corroborating estimates of exposure levels. Thus it can be used to justify a more robust epidemiological follow-up. Based on the highly regarded MN test typically employing blood cells to quantify exposure to genotoxins, the lens MN assay would be applied to lens epithelial fragments (tags) removed from surgical cataract patients who had resided near, or worked in, locales in which there existed a potential for radiation exposure. The unique biology of the lens complements the test by dramatically extending the duration (up to a working lifetime) over which Mns can express and can provide a cumulative record over that time-frame. In order to optimize the utility of the method, a dose-response calibration is required in a dose-defined population. We propose to calibrate the Lens MN Assay against dose by using tags removed from an epidemiologically and dosimetrically well-defined subset of workers at the Chernobyl site, the clean-up crews or "Liquidators". The study will involve 600 of the 130,000 Liquidators who worked on site during the period from the time of the accident (April, 1986) through February, 1987. Lymphocytes from a subset of the 600 will be also be assessed by the FISH-translocation assay to confirm the overall dosimetry and allow the comparison of the Lens MN assay against another, more established, bioindicator. The lens MN test imposes little burden on individuals in populations being surveyed since cataract extraction is a necessary, and extremely common surgical procedure. The recovery and proper handling of the tissue does not require additional expertise on the part of the surgeon nor does it extend the length of the operation. In addition, its relatively low cost, speed, and quantitative, long-term integrative capability, all recommend this biomarker for primary dose reconstruction in individuals, as well as communities in the United States, at risk from radiation hazards. Finally, it can serve to validate whether or no the cataracts which occasion the tag removal are the result of radiation exposure either in the workplace or from environmental sources.